David Epstein Interview

Why Your DNA Says You Can't Be Usain Bolt

MM: You mention at one point that these findings may change the way sports fans look at elite athletes. How do you think their perceptions will change?DE: Some people have asked me whether I think pulling back the curtain on some of the science ruins some of the magic in watching sports. I don’t feel that way at all. For me, I didn’t think that there was a level playing field. If we really wanted to see a level playing field, we would race identical twins only. We know that people have different genes. As a sports fan, one of the most influential things to me was realizing how specialized body types have become for certain athletic niches and that many more people are now ruled out of being elite athletes simply based on their body type, right from the get-go. That might be a little bit depressing, but to me, sports is like the coolest stage for examining human biological diversity that has ever existed.

MM: Do you think we’ll end up in a world where genetically gifted kids are tagged as future all-stars, dividing kids into two groups?DE: I sort of worry about that. There are, for example, certain genes that can tell you that you’re going to improve more rapidly than the next person with endurance exercise. Scientists are looking at those genes for medicine so they can tell people, "You need this health effect, you can get it really easily with x amount of running — and you maybe can’t, and need to be medicated." I do worry, because parents are pretty zealous. They’re already using genetic tests even though it’s mostly rubbish. My hope would be that the testing works in a way where you say to someone, "You can do whatever you want, but just so you know, you would improve very rapidly in this other thing."

MM: You wrote about the gene you carry that likely helped you improve faster than your running peers. If and when you have kids of your own, will you have them tested for sports genes?DE: That’s a good question because for the most part, I would say "no" for my kids. It probably could have saved me a little time, had I known. I got into running when I broke my arm playing football. I almost quit because I was so far behind my training partners when I got to college that I thought it was hopeless. It would have been nice if someone could have assured me that, "You will improve, you just need to stick with it for a couple months." I didn’t quit, anyway. For my kids, I think I would not. The only thing I would get them tested for at this point — assuming no history of sudden death in my family, because then I’d get them tested for some of these sudden-death genes — is a gene that we now know predisposes people to having permanent brain damage if they take a lot of hits to the head, whether it’s in hockey or football or boxing. If they had that gene, I would think about trying to mandate they not play football, because you’re just at so much increased risk, and it’s your brain.

MM: Say someone reading this wants to understand his own genetic profile as it relates to sports. Is there a test that’s readily available that works?DE: There’s a limited amount of testing available. When I got my aerobic responder genes tested, I used a commercial testing service called 23andMe, which gives you a report and they tell you about some genes they think are interesting. They also give you a bunch of raw data that you can download. I took that data to the lab that discovered the gene that I was writing about and I had them analyze it. So that was not something that was consumer-available, it was something I did as a reporter. There are all of these genetic testing companies coming online that are being marketed to parents for their kids and the most common gene they test for is ACTN3, which codes for protein found only in fast-twitch muscle fibers — the kind for sprinting and jumping. If you don’t have the so-called "right" version for sprinting, or at least one copy, you’re just not going to be in the Olympic 100-meter final. That’s a fact. But that only rules out 1 billion of 7 billion people on earth, so it’s really not a specific tool. You would do a better job taking your kid to the park and using a stopwatch than using that test.

MM: For weekend warriors, guys who go to the gym or run races, is there any value in testing?DE: The biggest value for weekend warriors is having a muscle biopsy, which tells you something about your genetics, but isn’t a test of your actual genes. You can find out your composition of fast-twitch to slow-twitch and in-between fibers — and that will give you a really good sense of what you’re best suited for. But you can figure that stuff out by trial and error. If you were always faster, quicker and had a good vertical jump compared to other people, you’ve probably got a healthy proportion of fast-twitch muscle fibers. If that’s you, you might get a bigger bang from high-intensity interval training and long periods of rest. Whereas if you’re way slow-twitch, you can train often, a lot and you won’t need as much rest.